Get Advice on Live Video Call
Earn $ Cash $ with
consultations on Bissoy App

A dryer is used for drying pears which has initial moisture content of 70 % (wet basis) and final moisture content of 5 % (wet basis). An experimental drying curve for the product indicates that the critical moisture content is 25 % (wet basis) and the time for constant drying is 5 min. Can you estimate the total drying time for product?

Correct Answer: 6.54 min
Initial product moisture content (Wo) = 0.7 / 0.3 = 2.33 kg (water) / kg (solids) Critical moisture content (Wc) = 0.25 / 0.75 = 0.333 kg (water) / kg (solids) Final moisture content (Wf) = 0.05 / 0.95 = 0.0526 kg (water) / kg (solids) Time for constant rate drying (tc) = 5 min Required Total drying time (Rc) = ((Wo) – (Wc)) / tc = (2.33 – 0.33) / 5 min = 0.4 kg (water) / kg (solids) min Falling rate drying time (tF) = (Wc)/Rc * ln ((Wc)/w) = 0.333/0.4 * ln (0.333 / 0.0526) = 1.54 min Total drying time (t) = 5 + 1.54 = 6.54 min

A solid is being dried in the linear drying rate regime from moisture content Xo to XF. The drying rate is zero at X = 0 and the critical moisture content is the same as the initial moisture Xo. The drying time for M = (Ls/ARc) is (where, L = total mass of dry solid, A = total surface area for drying Rc = Constant maximum drying rate per unit area X = moisture content (in mass of water/mass of dry solids)

200 kg of solids (on dry basis) is subjected to a drying process for a period of 5000 seconds. The drying occurs in the constant rate period with the drying rate as, Nc = 0.5 × 10-3 kg/m2.s. The initial moisture content of the solid is 0.2 kg moisture/kg dry solid. The interfacial area available for drying is 4 m2/1000 kg of dry solid. The moisture content at the end of the drying period is (in kg moisture/kg dry solid)

In a laboratory test run, the rate of drying was found to be 0.5 × 10-3 kg/m2.s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry basis. A tray dryer is used to dry 100 kg (dry basis) of the same material under identical conditions. The surface area of the material is 0.04 m2/kg of dry solid. The time required (in seconds) to reduce the moisture content of the solids from 0.3 to 0.2 (dry basis) is

A textile dryer is found to consume 4 m3 / hr of natural gas with a calorific value of 800 kJ/mole. If the throughput of the dryer is 60 kg of wet cloth per hour, drying it from 55% moisture to 10% moisture, estimate the overall thermal efficiency of the dryer taking into account the latent heat of evaporation only. Assuming the natural gas to be at standard temperature and pressure at which 1 mole occupies 22.4 liters and Latent heat of evaporation = 2257 kJ/K.

If the time taken for the moisture removal is obtained from the formula Time = Ss(Xc – Xe)/ Nc * A ln ((X1-Xe)/(X2-Xe)) then the falling curve will be curves symmetrically Where, Ss= Wet solid weight Xc,Xe- constant & equilibrium moisture content X1,X2 – initial and final moisture content

It takes 6 hours to dry a wet solid from 50% moisture content to the critical moisture content of 15%. How much longer it will take to dry the solid to 10% moisture content, under the same drying conditions? (The equilibrium moisture content of the solid is 5%).

Find the initial moisture content for the batch process if the final moisture content is 25% (dry basis) and the constant moisture content is 40%. (Includes constant and falling rate period)

Find the final moisture content for the batch process if the initial moisture content is 75% (dry basis) and the constant moisture content is 40%. (Includes constant and falling rate period)

Find the time taken to dry 50% to 40% of moisture (dry basis) if critical moisture content is 30%. If the weight of the wet solid is 5 kg and the product of area and the constant rate is 0.5 kg/min.

How many kilograms of cherry tomatoes are required to obtain 150 kg of dried cherry tomatoes with a final moisture content of 11% wet basis? The ripe cherry tomatoes used have a moisture content of 94% wet basis.